Clashes and shelling across Syria on Tuesday gave no indication that any letup in the violence was imminent, despite Monday's promise by the government of President Bashar al-Assad to withdraw its forces from population centers by April 10.

"We have seen no evidence today that he is implementing any of those commitments," State Department spokeswoman Victoria Nuland said. "We have been able to verify no withdrawal of mechanized units, which is what he's claiming credit for today."

"What we have seen since April 1st is not encouraging," U.S. Ambassador to the United Nations Susan Rice told reporters. "Should the government of Syria use this window -- rather than to de-escalate -- to intensify the violence, it will be most unfortunate, and it will be certainly our view that the Security Council will need to respond to that failure in a very urgent and serious way."

"It appears that Assad is escalating the violence," said Rafif Jouejati, a spokeswoman for the opposition Local Coordination Committees of Syria, which tallied at least 74 dead Tuesday. Thirty-three of the dead were in Idlib and 21 in Homs, where clashes were occurring between Free Syrian Army forces and the regime's army on the outskirts of the neighborhood of Baba Amr, the LCC said.

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There is no clarity on what will happen if Syria doesn't withdraw from cities by that date.

An advance team is headed into Syria to discuss the possible deployment of an observation team to monitor a cease-fire, Annan's office said. But at present, it's too dangerous for the task because of fighting.

Nadim Shehadi, associate fellow at the Middle East and North Africa Program of the London-based Chatham House, said Syria is playing games with the international community and "playing for time."

"I don't see them pulling out at all," he said Tuesday.

He said Syria has been trying to avoid passage of a binding and irreversible U.N. resolution that would provide for the use of force if needed, such as a Chapter VII resolution. To date, no U.N. action has been taken that has any teeth. The regime can live with condemnation under that circumstance and can survive civil war, he said.

Syria expert Joshua Landis, director of the Center for Middle East Studies and associate professor of Middle Eastern studies at the University of Oklahoma, said al-Assad recognizes that the "international community is working at cross-purposes," and he has exploited that.

The Annan plan is urging a cease-fire by the government and the opposition and a Syrian-led political process to end the crisis.

But countries such as those attending the Friends of Syria meeting in Istanbul are staunchly supporting the opposition forces and envision a Syria without al-Assad at the helm.

"They are gunning for him," Landis said. So, how can he slow down the effort to organize his overthrow? Back Annan's efforts, he said.

"Assad has negotiated this so all sides have to stop shooting," said Landis, who says he doubts there will be traction on troop withdrawal.

If opposition fighters continue their activity, al-Assad will say he has to guarantee the safety of citizens, and as long as "these terrorists are shooting," his forces have to defend the safety of citizens, Landis said. "That's what his line has been."

"He's going to say, 'I can only stop shooting when the revolutionaries stop shooting.'"

"The rebels will keep shooting, and the Syrian army will keep targeting them. Both sides believe they can win, and both sides believe time can be on their side," Landis said. "That doesn't promote compromise."

Syria's withdrawal announcement came the same day that Russia pressured Damascus to withdraw its troops. Russia and China have vetoed U.N. Security Council attempts to condemn the al-Assad regime

"If the withdrawal of troops is not accompanied by similar actions of those who fight against the Syrian government, I believe that no results will be yielded soon," said Foreign Minister Sergey Lavrov, according to the state-run Itar-Tass news agency.

Andrew J. Tabler, a Syria expert at the Washington Institute for Near East Policy, said al-Assad may try to withdraw his troops from cities. But what happens next is key.

Protesters are sure to return to the streets, Tabler said. One of Annan's points urges Syrian authorities to "respect freedom of association and the right to demonstrate peacefully."

"Point six of the plan is for freedom of expression. Is he going to allow them to protest and demand the fall of the regime?" Tabler asked.

Tabler pointed out that al-Assad agreed to the Annan plan under Russian pressure. If the government doesn't take the appropriate steps, it could come under pressure from Moscow.

As for violence Tuesday, the military pounded opposition-held northern towns and clashed with defectors, activists said Tuesday.

The Syrian army shelled Binnish, Taftanaz and Taoum, and its helicopters fired on fleeing civilians, an opposition group in Binnish said.

"This is the most intense fighting we have witnessed thus far in Binnish since the beginning of the revolution," said Basher, an opposition activist who uses one name. "They are using helicopters and randomly firing on civilians in the cities."

Activists with the Local Coordination Committees of Syria reported shelling in Idlib and Homs, raids in the Damascus suburbs, mass arrests in Hama, raids in Hasaka and a siege on the city of Daraa.

A suspected militant group attacked the home of a military official, killing two of his bodyguards in Aleppo, the opposition Syrian Observatory for Human Rights said.

Annan's peace plan also addresses humanitarian aid and the plight of detainees -- two issues on the agenda of International Committee of the Red Cross President Jakob Kellenberger, who arrived Monday in Damascus for two days of meetings with top government ministers.

Among them was Foreign and Expatriates Minister Walid al-Moallem, according to SANA.

"Kellenberger voiced appreciation for the cooperation shown by the Syrian authorities, which allowed the Red Cross to reach areas affected by the current events and provide aid to those who need it," SANA said Tuesday.

Kellenberger also planned to visit areas affected by the fighting and observe the work of the Red Cross and the Syrian Arab Red Crescent.

''I am determined to see the ICRC and the Syrian Arab Red Crescent expand their presence, range and scope of activities to address the needs of vulnerable people," Kellenberger said before he arrived in Damascus. "This will be a key element of my talks with the Syrian officials."

The Red Cross has obtained greater access to many areas affected by fighting, a development it calls "positive."

Kellenberger is discussing an expansion of those activities, the implementation of a two-hour daily pause in fighting to distribute relief aid and greater access to detainees, International Committee of the Red Cross spokesman Hicham Hassan said.

"Visiting people who have been detained remains a priority for us," said Kellenberger, making his third visit to Syria since June. The Red Cross wants to interview detainees without the presence of security forces or other detainees, Hassan said.

The Syrian regime has consistently blamed "armed terrorist groups" for violence in Syria, but most reports from inside the country suggest the government is pummeling neighborhoods in an attempt to wipe out dissidents seeking al-Assad's ouster.

The United Nations has estimated at least 9,000 people have been killed in Syria since the unrest began more than a year ago, while opposition activists have put the toll at more than 10,000.